1. Field of the Invention
The present invention relates to a method of measuring a concentration of a material and a method of measuring a concentration of a dopant of a semiconductor device using the same. More particularly, the present invention relates to a method of measuring a concentration of a material contained in a boro-phosphorous silicate glass (BPSG) layer and a method of measuring a concentration of a dopant of a semiconductor device using the same.
2. Description of the Related Art
Recently, a degree of integration in semiconductor devices has increased to provide for faster processing of increased amounts of information and various techniques have been developed to facilitate information processing for a rapidly growing information society. In order to form increased numbers of patterns on a semiconductor substrate, a distance between patterns decreases and a width of a pattern narrows to form patterns having a relatively large step portion.
Generally, integrated patterns formed during manufacturing of a semiconductor device are transistors and various metal wirings formed on the semiconductor substrate. These integrated patterns are conductive, thus an insulation layer to insulate neighboring conductive layers should be formed between each pattern.
When the insulation layer is formed on the conductive pattern, which is formed on the semiconductor substrate, an upper surface of the insulation layer becomes uneven and crooked due to large stepped portions of the underlying patterns. Accordingly, when the conductive patterns and the insulation layers are repeatedly formed on the underlying patterns and layers, the unevenness of the layers formed later becomes significant, ultimately resulting in a formation of a device that does not function as a semiconductor device. Therefore, a method of forming an insulation layer filling gaps between patterns having large stepped portions and narrow intervals without forming internal voids and accomplishing planarization is an important technique.
An insulation layer is formed by depositing boro-phosphorous silicate glass (BPSG) because the gap-filling property or the planarizing property is improved by heating the deposited layer. A thus-formed BPSG layer has a good reflowing characteristic accompanying a property of changing viscosity rapidly through heating at a temperature of about 850xc2x0 C. The planarizing degree of the BPSG layer is different depending upon the concentration of dopants contained in the BPSG layer at an identical temperature. Therefore, BPSG insulation layers having different dopant concentrations exhibit different insulating properties.
In order to lower a processing temperature during semiconductor processing, a concentration of dopants, such as boron (B), phosphorus (P) and the like, in silicon oxide (SiO2), which is a primary component of the BPSG layer, is controlled to accomplish a good planarizing property at a low temperature. Accordingly, the measure of the intensity of the dopants, including boron and phosphorus, in the BPSG insulation layer is a very important inspection step.
A Fourier Transform Infrared Ray measurement (FT-IR measurement) may be used to analyze components contained in a layer.
A measuring instrument of an FT-IR analyzer is used for performing the FT-IR measurement. An absorption intensity distribution of IR for a target material is illustrated as a spectrum. When a radiant light passes through a layer of solid, liquid or gas, electrons, composing an atom, a molecule or an ion, absorb the radiant light to be transferred to an energy level corresponding to an absorbed photon energy of the radiant light. The difference between the electron energy levels is inherent to each chemical species. Therefore, the species composing the target material can be analyzed by inspecting a frequency of the absorbed radiant light. The frequency (c) is represented by an equation of c=xcexd/xcex. In this equation, xcexd represents a transferring velocity of a wave having a constant period and xcex represents a wavelength. An IR spectrum is illustrated by means of a wave number that is a reciprocal number of the wavelength.
In order to measure a concentration of each material included in a sample, a peak area at a peak region illustrated by each material in the IR spectrum is utilized. That is, the concentration of each material included in the sample may be noted by a relative size of the peak area illustrated by each material.
However, since a diameter of a measuring beam of the instrument is about 10 mm or larger, the beam is reflected and scattered by patterns formed on a substrate when the measurement is carried out on a BPSG layer formed on a semiconductor substrate. A distortion of the peak area due to the patterns is even more severe as a thickness of the BPSG layer increases.
In order to measure a concentration of a dopant in a BPSG layer during a semiconductor processing, a test sample is used. The test sample is obtained by forming a BPSG layer on a bare substrate using the same conditions as in the manufacturing process of the device. Then, the thickness and the concentration of the dopant are measured for the test sample and those of the BPSG layer are calculated using the measured result.
The test sample is formed considering various parameters to maintain the same state with a BPSG layer formed during actual semiconductor processing. However, when the sample is thick or when the intensity of the dopants in the sample is large, the intensity of the light transmitting the sample is insufficient so that detecting the transmitted light is difficult. In this case, the absorption intensity distribution is not illustrated clearly and a large numbers of split peaks are illustrated as noise around a main peak representing a specific material. Accordingly, the peak area cannot be calculated to precisely determine a concentration deviation. Thus, obtained data are unreliable.
In addition, a defect test and a concentration measurement for each processing step should be separately implemented, which increases overall processing time. Further, an additional process of forming the test sample must be implemented for every step of forming the BPSG layer during the semiconductor processing thereby increasing a manufacturing cost of the semiconductor device.
A first feature of the present invention is to provide a method of measuring concentration of a dopant using an infrared measurement, thereby obtaining reliable data even when an intensity of a transmitted light is small.
A second feature of the present invention is to provide a method of measuring concentration of a dopant using an infrared measurement, by which reliable data can be obtained even when an intensity of the transmitted light is very small thereby providing an unclear spectrum for some materials.
A third feature of the present invention is to provide a method of measuring concentration of a dopant of a semiconductor device, which can be repeatedly performed every time an insulation layer, including a dopant, is formed.
A fourth feature of the present invention is to provide a method of measuring concentration of a dopant of a semiconductor device, which can be applied along with actual semiconductor processing.
In accordance with a first aspect of the present invention, there is provided a method of measuring a concentration of a material including irradiating an infrared light onto a semiconductor substrate having a layer formed thereon, the layer including a first material and a plurality of dopants of which an entire intensity is less than an intensity of the first material, wherein a portion of the infrared light is absorbed in the semiconductor substrate including the layer and a remaining portion of the infrared light is transmitted through the semiconductor substrate including the layer; computing intensities of the infrared light absorbed in the first material and the plurality of dopants in accordance with light wave numbers by utilizing a difference between an entire intensity of the infrared light and an intensity of the infrared light transmitted through the semiconductor substrate including the layer and by utilizing a difference between an entire intensity of the infrared light absorbed in the semiconductor substrate including the layer and an intensity of the infrared light absorbed in only the semiconductor substrate; observing light wave number regions respectively corresponding to predetermined intensities of the infrared light absorbed in the first material and the plurality of dopants among all the light wave number regions absorbed in the first material and the plurality of dopants; and obtaining concentrations of each of the plurality of dopants by utilizing a ratio of the light wave number regions corresponding to the predetermined intensities of the infrared light absorbed in each of the dopants with respect to the light wave number region corresponding to the predetermined intensity of the infrared light absorbed in the first material.
In accordance with a second aspect of the present invention, there is provided a method of measuring a concentration of a material including irradiating an infrared light onto a semiconductor substrate having a layer formed thereon, the layer including a first material and a plurality of dopants of which an entire intensity is less than an intensity of the first material, wherein a portion of the infrared light is absorbed in the semiconductor substrate including the layer and a remaining portion of the infrared light is transmitted through the semiconductor substrate including the layer; computing intensities of the infrared light absorbed in the first material and the plurality of dopants in accordance with light wave numbers by utilizing a difference between an entire intensity of the infrared light and an intensity of the infrared light transmitted through the semiconductor substrate including the layer and by utilizing a difference between an entire intensity of the infrared light absorbed in the semiconductor substrate including the layer and an intensity of the infrared light absorbed in only the semiconductor substrate; observing light wave number regions respectively corresponding to predetermined intensities of the infrared light absorbed in the first material and the plurality of dopants among all the light wave number regions absorbed in the first material and the plurality of dopants; and obtaining concentrations of each of the plurality of dopants by utilizing a ratio of the intensity of the infrared light absorbed in each of the plurality of dopant corresponding to an entire light wave number regions with respect to the light wave number region corresponding to the predetermined intensity of the infrared light absorbed in the first material.
Preferably, the first material includes silicon and the plurality of dopants include boron and phosphorus. In addition, a plurality of conductive patterns may be formed on the semiconductor substrate.
The method may further include measuring an intensity of the infrared light absorbed in the semiconductor substrate, prior to forming the layer including the first material and the plurality of dopants on the semiconductor substrate.
In accordance with a third aspect of the present invention, there is provided a method of measuring concentrations of dopants in a semiconductor device including forming a plurality of conductive patterns on a semiconductor substrate; forming a first BPSG layer on the semiconductor substrate including the conductive patterns; irradiating a first infrared light onto the semiconductor substrate including the conductive patterns and the first BPSG layer, wherein a portion of the first infrared light is absorbed in the semiconductor substrate including the conductive patterns and the first BPSG layer and a remaining portion of the first infrared light is transmitted through the semiconductor substrate including the conductive patterns and the first BPSG layer; computing intensities of the first infrared light respectively absorbed in dopants included in the first BPSG layer in accordance with first light wave numbers by utilizing a difference between an entire intensity of the first infrared light and an intensity of the first infrared light transmitted through the semiconductor substrate including the conductive patterns and the first BPSG layer, and by utilizing a difference between an entire intensity of the first infrared light absorbed in the semiconductor substrate including the conductive patterns and the first BPSG layer and an intensity of the first infrared light absorbed in only the semiconductor substrate including the conductive patterns; and obtaining concentrations of a first boron dopant and a first phosphorus dopant by utilizing a ratio of the first light wave number regions corresponding to predetermined intensities of the first infrared light absorbed in the first boron dopant and the first phosphorus dopant of the first BPSG layer with respect to the first light wave number region corresponding to a predetermined intensity of the first infrared light absorbed in a first silicon of the first BPSG layer.
The method may further include forming a second BPSG layer on the first BPSG layer of which concentrations of the first boron and the first phosphorus are obtained; irradiating a second infrared light onto the semiconductor substrate including the second BPSG layer, wherein a portion of the second infrared light is absorbed in the semiconductor substrate including the second BPSG layer and a remaining portion of the second infrared light is transmitted through the semiconductor substrate including the second BPSG layer; computing intensities of the second infrared light respectively absorbed in a second silicon, a second boron dopant and a second phosphorous dopant included in the second BPSG layer in accordance with second light wave numbers by utilizing a difference between an entire intensity of the second infrared light and an intensity of the second infrared light transmitted through the semiconductor substrate including the second BPSG layer, and by utilizing a difference between an entire intensity of the second infrared light absorbed in the semiconductor substrate including the second BPSG layer and an intensity of the second infrared light absorbed in only the semiconductor substrate including the conductive patterns and the first BPSG layer; and obtaining concentrations of the second boron dopant and the second phosphorus dopant by utilizing a ratio of the second light wave number regions corresponding to predetermined intensities of the second infrared light absorbed in the second boron dopant and the second phosphorus dopant included in the second BPSG layer with respect to the second light wave number region corresponding to a predetermined intensity of the second infrared light absorbed in the second silicon of the second BPSG layer.
The measuring of the concentration of a dopant may be repeatedly performed more than twice.
In accordance with a fourth aspect of the present invention, there is provided a method of measuring concentrations of dopants in a semiconductor device including selecting a sample of a semiconductor substrate on which a BPSG layer is formed during a semiconductor device manufacturing process; obtaining an intensity of an infrared light absorbed in the BPSG layer formed on the sample with respect to a wave number of the infrared light; and obtaining concentrations of boron and phosphorus included in the BPSG layer formed on the sample by utilizing a ratio of light wave number regions corresponding to a predetermined intensities of the infrared light absorbed in the boron and the phosphorus with respect to a light wave number region corresponding to a predetermined intensity of the infrared light absorbed in a silicon included in the BPSG layer.
In the above method, when the concentrations of the boron and the phosphorus included in the BPSG layer as acceptable as required for the semiconductor device manufacturing process, the semiconductor device manufacturing process proceeds with the sample. In the alternative, the above method may further include removing the BPSG layer and forming a new BPSG layer including boron and phosphorus having newly adjusted concentrations on the semiconductor substrate when the concentrations of the boron and the phosphorus included in the previous BPSG layer is not acceptable as required for semiconductor device manufacturing process.
According to the present invention, additional manufacture of a test sample is not required to measure a concentration of a dopant, which decreases a processing cost. In addition, a thickness of a layer and the concentration of the dopant included therein can be measured simultaneously, which reduces a processing time.